1 Protein Localization

Protein localization

determines protein function based on its position in the cell

Membrane-enclosed organelles

compartments with specific locations in the cytosol

Nuclear pore

opening in nuclear envelope regulating molecule transport

Cis face

receiving side of Golgi oriented toward ER

Trans face

exit side of Golgi oriented toward plasma membrane

Protein translocation

movement of proteins across membranes via translocators

Protein translocators

membrane proteins that assist protein movement

Gated transport

movement through selective gates such as nuclear pores

Vesicular transport

transport using membrane-bound vesicles

Autophagy

engulfment process forming compartments for degradation or transport

Signal sequence

continuous amino acid sequence directing proteins to specific destinations

Sorting receptor

protein recognizing signal sequences

Signal patch

3D arrangement of amino acids formed after folding

Sorting signal

sequence or structure directing protein localization

Bidirectional transport

continuous movement between cytosol and nucleus

Nuclear envelope

double membrane enclosing the nucleus

Inner nuclear membrane

membrane layer binding chromatin and nuclear lamina

Outer nuclear membrane

membrane continuous with ER and studded with ribosomes

Perinuclear space

space between nuclear membranes continuous with ER lumen

Nuclear pore complex

structure regulating transport between nucleus and cytosol

Nucleoporins

proteins composing nuclear pore complex

Nuclear lamina

protein network providing structural support

Nuclear lamins

cytoskeletal proteins forming lamina

Aqueous channel

pore allowing diffusion of small molecules

Passive diffusion

movement of small molecules without energy

DNA polymerase

enzyme requiring nuclear entry for DNA replication

RNA polymerase

enzyme required for transcription in nucleus

Transcription factor

protein regulating gene expression

Histones

proteins associated with DNA packaging

Recognition signal

sequence required for nuclear entry

Transport receptor

protein mediating nuclear transport

Energy requirement

need for GTP or ATP in transport processes

Nuclear localization signal

sequence directing proteins into nucleus

Positively charged amino acids

lysine and arginine residues in NLS

Nuclear import receptor

protein binding NLS and nucleoporins

Karyopherin

family of nuclear transport receptors

FG repeats

nucleoporin sequences serving as binding sites

Nuclear import

process of transporting proteins into nucleus

Ran protein

small GTPase acting as molecular switch

Ran-GTP

active GTP-bound form of Ran

Ran-GDP

inactive GDP-bound form of Ran

GTP hydrolysis

conversion of GTP to GDP releasing energy

GTPase-activating protein

protein stimulating GTP hydrolysis

Guanine nucleotide exchange factor

protein exchanging GDP for GTP

Molecular switch

protein cycling between active and inactive forms

Nuclear export

transport of proteins out of nucleus

Transport cycle

sequence of steps in nuclear transport

Cargo protein

protein being transported

Receptor-cargo complex

binding of transport receptor to cargo

Nucleocytoplasmic transport

movement between nucleus and cytoplasm

Selective permeability

controlled passage through nuclear pores

Small water-soluble molecules

molecules that diffuse freely through NPC

Large macromolecules

require active transport through NPC

Protein targeting

directing proteins to specific locations

Cellular compartmentalization

separation of cellular processes into organelles

Cytosol

fluid portion of cytoplasm

Organelle localization

specific positioning of organelles in cell

Protein destination

final location of a protein

Transport specificity

accuracy of protein targeting

Transport pathway

route taken by proteins within the cell

Signal recognition

detection of targeting signals

Transport efficiency

effectiveness of protein movement

Protein function

activity determined by location

Intracellular transport

movement within the cell

Membrane barrier

lipid bilayer restricting movement

Selective gate

structure controlling entry and exit

Transport regulation

control of protein movement

Transport machinery

proteins involved in movement

Protein routing

directing proteins to destinations

Cellular organization

arrangement of structures within cell

Protein trafficking

overall process of protein movement

Transport directionality

movement toward specific destination

Compartment identity

unique characteristics of organelles

Protein sorting

distribution of proteins to correct locations